• Journal of Korean Society on Water Environment
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• v.22 no.5
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• pp.926-932
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• 2006

A series of bench-scale membrane filtration experiments were performed to systematically investigate the removal mechanisms of reverse osmosis (RO) and nanofiltration (NF) membranes for BTEX (benzene, toluene, ethylene, xylene), trichloroethylene (TCE) and tetrachloroethylene (PCE). The molecular weight of these organic compounds ranged from 78 to 166 dalton. The rejection of organic compounds by RO/NF membranes varied significantly from 59.6 to 99.2% depending on solute and membrane types. Specifically, experimental results demonstrated that the removal efficiency of RO/NF membranes increased as solute molecular characteristics such as W/L (molecular width/length) ${\times}$ $M_W$ (molecular weight) and octanol-water partition coefficient increased. This observation suggested that the rejection of small organic compounds by RO/NF membranes was determined by the combined effect of physical (molecular size and shape) and chemical (hydrophobicity) properties.

• Korean Journal of Ecology and Environment
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• v.42 no.4
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• pp.487-494
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• 2009

We compared spatial and temporal variations of water chemistry between high-flow year ($HF_y$) and low-flow year ($LF_y$) in an artificial lentic ecosystem of Daechung Reservoir. The differences in the rainfall distributions explained the variation of the annual inflow and determined flow characteristics and water residence time and modified chemical and biological conditions, based on TP, suspended solids, and chlorophylla, resulting in changes of ecological functions. The intense rainfall and inflow from the watershed resulted in partial disruption of thermal structure in the metalimnion depth, ionic dilution, high TP, and high suspended solids. This condition produced a reduced chlorophyll-a in the headwaters due to low light availability and rapid flushing. In contrast, reduced inflow and low rainfall by drought resulted in strong thermal difference between the epilimnion and hypolimnion, low inorganic solids, high total dissolved solids, and low phosphorus in the ambient water. The riverine conditions dominated the hydrology in the monsoon of $HF_y$ and lacustrine conditions dominated in the $HF_y$. Overall data suggest that effective managements of the flow from the watershed may have an important role in the eutrophication processes.

• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.3
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• pp.270-276
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• 2014

Seasonal characteristics of water and sediment qualities and potential effects of the freshwater discharge from a small tide embankment interior in a coastal area in Goheung county were investigated from May to September in 2012. Chemical oxygen demand values (COD) were mostly higher than 2 mg/L in summer ebb tide, which exceed the standard value of water quality criteria II of acceptable level for aquaculture activities. Nitrogen and phosphorus were found as the limiting nutrients for algae growth in summer and fall and in spring, respectively. Nitrogen was the limiting nutrient for diatom growth in the whole studied period. The sudden high values of COD, ammonia, dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP) were found in water sample collected from station 5 which located in front of the tide embankment sluice gate during spring ebb tide. The freshwater discharge form the tide embankment interior maybe affected the survey areas during a short time interval. Mean values of eutrophication index of the surveyed coastal region in spring, summer and fall were all bigger than 1. Water quality was mostly considered at level II which acceptable for aquaculture activities. Sediment quality in this study was generally in the range of standard for fisheries environment.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.389-394
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• 2008

Nowadays Plate Heat Exchanger (PHE) is widely used in different industries such as chemical, food and pharmaceutical process and refrigeration due to the efficient heat transfer performance, extreme compact design and efficient use of the construction material. In present work, PHE is applied in the fresh water generator system. Fresh water generators or desalinators are installed in ship to convert seawater to fresh water using heat from engines. PHE is an important part of a condensing or evaporating system. Among many of factors which should be concentrated on, the heat transfer and pressure drop is most important parts during sizing and rating the performance of PHE. Flow maldistribution is common but it will significantly reduce the heat exchanger performance. In this paper provide a overview of PHE cover basic of theory and conduct a numerical approach for flow distribution in plate channel. An experimental study on the performance of fresh water generator system which developed by plate heat exchanger will presented in future research. Thus, extensive experiment and analysis is required to study the thermal and fluid flow characteristics of PHE.

• Corrosion Science and Technology
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• v.19 no.2
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• pp.66-74
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• 2020

In this paper, the author's team has carried out a comparative experimental study on the corrosion characteristics of Q235 steel commonly used in large-scale storage tanks under the specific bottom water environment found with Russian and Daqing crude oil. It was found that there is a certain degree of uniform or local corrosion on the tank floor depending on the kind of bottom water. The bottom water corrosion of Daqing crude oil is a uniform corrosion caused by carbon dioxide. While the Russian crude oil bottom water corrosion is clearly local corrosion caused by co-corrosion of carbon dioxide and hydrogen sulfide, here the corrosion rate is obviously higher than that caused by Daqing crude oil. There are two modes of storage tank inspection and maintenance that have been currently adopted by Chinese refining and chemical enterprises: a regular inspection mode and a API581-2016 risk-based detection mode. These modes have been effectively combined to form an intelligent tank inspection and maintenance mode, software tools to support this intelligent inspection and maintenance management have been developed.

• Macromolecular Research
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• v.13 no.4
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• pp.339-343
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• 2005

Microbial hydrogel was prepared by ${\gamma}-irradiation$ of poly(${\gamma}-glutamic acid$) (PGA) which was produced from Bacillus subtilis BS 62 and it's physico-chemical characteristic was examined. The hydrogel, prepared from 10% PGA with the dose of 48 kGy, was swollen up to 1,370 times of specific water content as dry weight basis. The hydrogels obtained above the dose of 48 kGy appeared to have higher compressive strength but lower specific water content. The period to reach a swelling equilibrium for the hydrogel in deionized water at the temperature range of 4 to $45^{\circ}C$ was about 10 h. The swollen hydrogel was shrunk in ionic solutions with the increase of ionic strength, and the rate of shrinkage was greater in calcium chloride solution than in sodium chloride. Specific water content of the hydrogel was quickly decreased at $80^{\circ}C$, showing a thennally hydrodegradable property.

• Journal of Korean Society of Water and Wastewater
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• v.27 no.5
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• pp.621-629
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• 2013

Since algae had been issued an environmental problem, water blooms, deepened due to increase of retention water basin in Korea as well as a biomass resource for producing biofuel, this study conducted a series of experiments for Spirulina platensis using the flotation process with micro-bubble. To elevate utilization of collected-algae, this study focused on omitting or minimizing coagulant's doses as changing a cultivation period and condition affected on physical property change of algae. Two coagulants, PAC and Chitosan, were used to test the collecting rate of algae and the result found no difference between two rates. For flotation experiments without adding the coagulant, dried algae weight (passing 14 days after cultivation for 20 days) detected high separation efficiency 98.2 % and it (passing 7 days after long-term cultivation for 28 days) presented good separation efficiency 91.9 %. Chlorophyll's separation efficiency showed a similar tendency with the case of the dried algae weight. In endogeny conditions, a light source and a carbon source were not considerably affected on the flotation separation efficiency. Thus, this study confirms that algae biomass may be collected without the coagulant during the endogeny condition period after enough cultivation time, 3 weeks.

• Journal of Welding and Joining
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• v.34 no.4
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• pp.17-22
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• 2016

In this study, we compared the physical and chemical properties evaluation for each size in the SUS316L metal powder produced by water atomization and gas atomization. and we analyzed the experimental data in order to find the basis of a suitable metal powder (SUS316L) for DED (Direct Energy Deposition) processing. Also it evaluated the properties of each layered surface and cross section according to the number of deposition and deposition speed. In the result of optical microscopy measurements, the metal powder by water atomization was the crack generated between the deposition layer, the deposition layer was poor quality. However, metal powder by gas atomization was obtained a relatively good deposition results than metal powder by water atomization.

• The Korea Journal of Herbology
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• v.29 no.6
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• pp.1-6
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• 2014

Objectives : This study was aimed to compare Gyejibokryeong-hwan (GBH) decoctions produced using different pressure levels for various extraction times to find the optimal extraction conditions through extraction yield, total soluble solids content (TSSC), hydrogen ion concentration (pH), and the contents of chemical compounds. Methods : Decoctions of GBH were prepared under the pressure levels of 0 or $1kgf/cm^2$ for 30-180 min using water as extraction solvent. The extraction yield, TSSC, and pH were measured, and the amounts of the chemical compounds were determined using high performance liquid chromatography-photodiode array detector. Results : The higher pressure and longer extraction time increased the values of TSSC and extraction yield, while decreased the pH value. The decoctions produced in 180 min by pressurized method and produced in 150 min by non-pressurized method showed maximum values of extraction yield and TSSC with minimum value of pH. The amounts of chemical compounds showed variations in pressurized and non-pressurized decoction during overall extraction times. The influences of pressure and extraction time on extraction yield, TSSC, pH, and the contents of chemical compounds were confirmed by regression analysis, which showed that all extraction values were significantly affected by at least one of two extraction factors, pressure and extraction time. Conclusions : This study suggests that the pressure and extraction time can significantly affect the extraction efficiency of components from GBH decoctions. However, optimal extraction conditions could not be chosen due to the variation of the amounts of chemical compounds.

• Korean Journal of Environmental Agriculture
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• v.28 no.4
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• pp.333-339
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• 2009

Various cultural practices have been promoted as management options for enhancing soil quality and health. The use of soil management methods can cause changes in fertility by affecting soil chemical properties. This study aimed to evaluate interactions between soil chemical properties and soil management methods in protected cultivation, and to classify soil management methods that similarly affect soil chemical properties. Water-logging and irrigation reduced soil pH and available $P_2O_5$ content. Application of animal manures has a positive effect on levels of organic matter, Av.$P_2O_5$, K, Zn, and Cu. The electrical conductivites tened to be low in the application of organic amendments, including rice and wood residues. Deeper plowing caused a reduction in Ca content. Practicing soil nutrient-considering fertilization and fertigation did not exert an influence on nutrient element contents. In a cluster analysis of the soil management methods according to major nutrients, low similarities were found with deeper plowing and crop rotation with rice in comparison with other practices. In a cluster analysis by minor nutrient characteristics, crop rotation and application of animal manures and rice residues were linked at a high Ward's distance, while other practices were found to be relatively low distinct. Each soil management method has a similar or different effect on soil chemical properties. These results suggest the necessity of establishing limits and standards according to the effects of soil management methods on soil chemical properties for economic soil practices.